A wide variety of types of valves are currently used in a vast array of applications. One common type of valve is known as a gate valve. Gate valves have long been, and are today, extensively used to control the flow of fluids frequently under high pressure. Uses for gate valves include controlling the flow through pipes of steam, oil, water, gas, and other fluids. Such valves are used at selected points on pipelines, in plants and to control the flow of water into buildings and other facilities. A gate valve being used in a preset position is preferably secured in that position and, for this purpose, the hand wheel of the gate valve is often secured to the truss support or other stationary portion of the valve by a chain and padlock.
Unfortunately, certain people, or even organizations, are tempted to tamper with the settings of gate valves and to do so, the chain is cut or the staple of a padlock is sawed. Quite frequently, tampering with a gate valve to the extent of changing its setting, even to the extremes of shutting it off completely or fully opening it, may produce disastrous consequences. For example, if the flow of water to a building is shut off, none of its automatic sprinklers may work with the result that there would be no automatic suppression of a fire in the building. In the situation of a pipeline conducting the flow of oil or water, shutting off a gate valve may result in shutting down pumps or even causing damage to the pumps, which do not have means to respond to a flow stoppage.
One prior art device aimed at solving at least some of these problems is disclosed in U.S. Pat. No. 5,353,833, issued Oct. 11, 1994, and hereby incorporated by reference in its entirety. The locking device disclosed in that patent includes a bracket that is clamped onto a portion of the truss extending upwardly from the valve bonnet and supporting a gate valve stem and a hand wheel. In one embodiment, the bracket clamps onto only one of the truss members and in another embodiment it engages both of the spaced truss members by spanning across the stem packing components. The bracket in each embodiment has a rigid bar extending upwardly which is capped by an L-shaped member seated against the inside of the hand wheel and between an adjacent pair of the radially extending spokes of the hand wheel. The bracket may be secured by a cylindrical lock having a recess into which the vertical portion of the L-shaped member is inserted and then locked. The bracket may also be secured by a padlock.
Unfortunately, the locking device disclosed in U.S. Pat. No. 5,353,833 has certain shortcomings. Specifically, if the bracket only engages one of the truss members it is not securely mounted to the valve. The bracket is prone to movement on the truss and the hand wheel can be rotated even when the locking device is installed. The embodiment of the locking device which mounts to both of the truss members may offer a more secure attachment, but installation and removal is often difficult and cumbersome. Moreover, the bracket often interferes with the stem packing to loosen and/or damage those components resulting in leakage from the valve.
Additionally, many valve hand wheels have 3, 5 or 6 spokes spaced equally at about 120°, 72° or 60°, respectively. Even if the device in the '833 patent is installed correctly and securely, the vertical portion of the L-shaped member projecting between the spokes does not entirely prevent rotation of and tampering with the hand wheel. For example, if such a locking device is installed on a gate valve with a 3 spoke hand wheel, the hand wheel could still be rotated up to 120° causing an unauthorized adjustment to the valve before the locking device prevents further rotation and adjustment.
Therefore, a need exists for a secure, effective and easily implemented device to prevent the unauthorized, inadvertent or otherwise undesired manipulation and adjustment of gate valves that does not suffer from these and other problems associated with prior art locking devices.